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Triumph TR3 - negative or positive ground tr3

i am working on a friends tr3 for him. it is not charging and we suspect the generator. quick question, are these cars supposed to be negative or positive ground from factory? he told me it was positive ground, but it actually has the negative cable grounded. how are they supposed to be grounded? negative or positive?

The battery sits in the battery box to the rear of the engine block. The positive post (as it came from the factory) should be up to the rear near where the clutch resevoir is located if you have a left hand drive car - as in America. This + post is connected with a 6' long braided cable to be bolted to the firewall with a 7/16" UNF bolt, and washer. It is up behind where the pipe feeds the pressure to the oil gauge where it goes through the hole in the dashboard.

The neg post is the other one over to the carb side of the engine. The heavy power cable from this post is connected down to the solenoid 0r bendix starter located on the flat deck of the firewall just behind the #2 carb.

If you have it like this it should start. Or at least the starter should turn over.

Unless your battery is dead or a lot of other things meed attention.

Don Elliott, Original owner, 1958TR3A
Don Elliott

don, the car does start and run, it's just not charging. the owner told me it was a "positive ground" car. however, the negative side of the battery is bolted to the firewall, as a "negative ground" car would be. therefore i wondered if was supposed to be negative or positive ground. everything is working, the car starts and runs fine, it's just not keeping the battery charged. i suspect the generator or the regulator.

Hi Ricky,

Does yur amp gauge show if it's charging or discharging? Another issue, if it has in fact been changed to a negative ground car, but the PO did not rewire the amp gauge, it will show discharge when it is actually charging.

Good luck,
Danny Thomason

Take a look at the generator. If it is down low and painted black - it's a generator for pos. ground.

If it is all shiny and mounted up higher and is full of cooling slots, it's an alternator and the PO didn't tell you he put in an alternator. - This would have neg ground.

Check it out and maybe your alternator has a loose wire or like Danny wote, it may be really simple.

Don Elliott
Don Elliott

If they've added a later model radio, it probably will have to be left as a negative ground to keep it. I think you can still use the generator as a negative ground if you want to, but make sure all the wiring is right for that. You can check the generator for output real easy. I'll post directions from the book later. If that's good, it probably is the regulator. If it's a Lucas brand, you can clean them up (2 sets of points) and adjust to a certain extent. Of course, all the connections should be cleaned up.

My experience has been regulator problems for lack of charging, no telling what yours is for sure. Anyway, it's a good time to get the old girl back in shape.

i wanted to update everyone on the generator / charging issue. we installed a different generator tonight. i installed it, then polarized it as was outlined earlier, and it is charging perfectly. apparently it WAS changed over to negative ground, and apparently the old generator had just gone out.

thanks to all,

Glad to hear you got volts again. Stop back anytime, maybe some of us can simplify your repairs. Or confuse the heck outa ya..hehe.

This thread was discussed between 17/10/2004 and 19/10/2004

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